code: def test_add_remove_mutates_not_replaces():
      assert not Callback.active
  
      with Callback():
          assert Callback.active
  
      assert not Callback.active
  
file_path: dask/dask/tests/test_callbacks.py
imports: from __future__ import annotations
  from dask.callbacks import Callback
  from dask.local import get_sync
  from dask.threaded import get
  from dask.utils_test import add
label_desc: Use image node_id 5 for calling a global function with example usage: test_add_remove_mutates_not_replaces() without return types